1. Field of the Invention
The present invention relates generally to the selective harvesting of certain plants such as, for example, strawberry and other species and hybrids in the Fragaria genus, as well as raspberry and other species and hybrids in the Rubus genus. More specifically, the invention relates to an apparatus and method for removing unwanted plants, or unwanted portions of plants, from a plant bed to facilitate more effective harvesting of the desired plants or portions of plants. While the present invention has general applicability to all suitable plant types, including other species and hybrids in the Rubus and Fragaria genera, because of the broad application to raspberries and strawberries in particular, the present device and method will be detailed with respect to those illustrative plants.
2. Description of the Prior Art
Strawberry plants are commercially propagated by planting “mother plants” in rows and allowing those plants to produce and send out multiple stolons called runners. These horizontal runners are sent outward from the base of the strawberry plants. At variable distances, new strawberry plants called “daughter plants” form at the runner nodes. This is possible due to the strawberry plant's ability to form adventitious specialized roots at the nodes along a runner. Wherever these roots touch nutritious soil, they continue to grow into that soil and establish a new clonal plant, or daughter plant, that is genetically identical to the mother plant that originally formed the runners. These vegetatively propagated plants may be subsequently harvested to be sold to commercial growers producing fruit for consumption.
After adequate chilling below 45° F., the plants start to go dormant and are harvested. The daughter plants will eventually be marketed to commercial growers and transplanted to produce fruit for sale. Under current harvesting practices, all of the plants, including mother and daughter plants alike, are dug, gathered together, and transported en masse to a processing facility where the mother plants are removed from the daughter plants and the daughter plants are graded and packed. The mother plants are discarded.
To date, the separating of the mother plants from the daughter plants, the disposing of the mother plants, and the sorting and packing of the daughter plants, has all been performed manually. Advances in computer-controlled vision and sorting techniques have enabled some mechanical sorting of these plants in the packing shed, thus reducing the significant amount of manual processing required for this sort/pack process. Unfortunately, existing technology has not advanced to the point where a computer vision system can, with 100% accuracy, determine the difference between mother and daughter plants. Allowing some mother plants to escape detection during the computer controlled sorting process greatly reduces the cost effectiveness and efficiency of this automated process because the resulting mother plants must still be removed by human hands.
With the widespread implementation of GPS guidance systems on agricultural tractors, it is now possible to guide an implement (for example a mother plant transplanting machine) along a planting line to sub-inch accuracy. Additionally, these GPS guidance systems have the capability to store this guidance information and allow the tractor and/or implement to go back to the same field at a later date (for example when strawberry plants are ready to be harvested), locate the previous plant line, and follow it with the same level of sub-inch accuracy.
Therefore, using this precise guidance system, the mother plants may be removed from their location in the field before the field is harvested. If these plants can be removed, destroyed, or rendered unharvestable in the field such that the plants are not mixed with the daughter plants, the sorting and packing operation is greatly simplified and the accuracy and through-put of the computer-controlled sorting system is greatly enhanced. As an added benefit, removing the mother plants prior to harvest may provide added benefit to the daughter plants by forcing them to increase root growth as nutrients are no longer being supplied by the mother plants. Finally, if the mother plants can be pulverized and buried with clean soil prior to the harvesting of the daughter plants, further handling and disposal of the mother plants is not required.
Raspberry cultivars readily produce new shoots from the roots of the raspberry plant. In a planting process called “suckering,” new nursery plantings are established by taking advantage of the plant's ability to produce these suckers. Commercial nurseries grow plants and harvest roots to supply the plantable rootstocks to fruit growers. As the plants destined for rootstock go dormant in the fall, they are harvested. Prior to the root harvesting process, the dormant plants are mowed down to a height that leaves only a short length of cane protruding from the surface of the planted bed of soil. This short length of cane and the associated woody portion of plant material that forms the transition from cane to roots, the “crown,” is left in the bed, and is currently harvested along with the roots. Current practice requires that these crowns be removed as a secondary operation in the packing shed. The crown removal process is currently performed manually. This is a time-consuming and expensive process.
The present invention eliminates the secondary separation operations described above with respect to strawberries and raspberries. The invention mechanically removes unwanted strawberry mother plants or portions of mother plants in situ, before the harvesting operation. The invention may also be used to remove raspberry crowns from a plant bed before the roots are harvested. Similar objectives may be achieved with other plants.